Soil School: Soil tests show P, K and S levels trending lower as removal rates exceed replacement

Soil test results from across North America show levels of several key crop nutrients are generally trending lower — a sign that nutrient removal rates are exceeding the replacement of those macronutrients, potentially limiting crop yields.

For example, 46 per cent of soil samples from across North America tested below the critical level of phosphorus (P) in 2020 — a 5 per cent increase from 2001, explains Treyston Beyrer, crop nutrition lead for Mosaic, in this latest Soil School episode looking at trends in crop nutrient uptake, removal and replacement.

According to analysis done by The Fertilizer Institute looking at around 25 million soil samples submitted to public and private labs between 2001 and 2020, the median soil test P level across North America has declined by about 0.5 parts per million per year.

The percentage of soil samples with potassium (K) and sulfur (S) levels below thresholds recommended by relevant university, state, or provincial soil fertility guidelines has also noticeably increased over the past two decades, notes Beyrer, as shown in the slides in the video below.

"There are are different reasons why we see that," he explains. "One is nutrients, fertilizer rates not being applied with crop removal. And the other thing is, many of us have been stuck in a routine of applying the same rates over a number of years. And over that same time frame, we see that the nutrient removal has increased. Our crop yields have gone up."

Since nutrient uptake and removal can be unique to specific geographies, Beyrer recommends working with a local agronomist or retailer to better understand what's happening with nutrient levels. As a guideline, Mosaic has compiled data from universities and government research to create a chart with uptake and removal rates for all the major crops and nutrients applied in North America (Find the chart at RealAgriculture.com.)

Dig into what's happening with crop nutrient removal and replacement, and why soil tests show levels of some key nutrients trending lower, in this new Soil School episode with Tryston Beyrer of Mosaic.

Website: https://www.realagriculture.com/

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